Electronic spectra of complexes

As we saw in Chapter 2, electron-electron repulsions cause a given electron configuration to be split into terms. However, for the simplest case, d. there will be no such splitting of the free ion levels because there is only one electron. Thus we have only one term, the ground state D, because the five d orbitals are degenerate and the electron has an equal probability of being in any one of them. As we have also seen previously, these five d orbitals will, under the influence of an octahedral field (either weak or strong), be split into r K and et orbitals. The D term likewise will be split into 

The wave functions for S. P, D, F, etc. terms have the same symmetry as the wave functions for the corresponding sets of s, p, d.f, etc. orbitals. This means that a D term is split by an octahedral field in exactly the same manner as a set of d orbitals 

An inverse relationship also exists between fields of octahedral and tetrahedral symmetries. We saw earlier in this chapter that crystal fields of these two symmetries produce inverse splitting patterns for one-electron d orbitals. This relationship also holds when electron-electron repulsions are added to the picture any free-ion term will be split into the same new terms (except for g and u designations, which are inappropriate for tetrahedral complexes) by tetrahedral and octahedral fields, but the energy ordering will be opposite for the two symmetries. 

In order to use the correlation diagrams shown in Ftg. 11.37 or simplifications of them, it is necessary to know the selection rules that govern electronic transitions. 

Selection rules reflect I he restrictions on state changes available to an atom or molecule. Any transition in violation of a selection rule is said to be forbidden, but as we shall see, some transitions are mote forbidden than others (to paraphrase George Orwell40). We shall not pursue the theoretical bases of the rules in any detail but merely outline simple tests for their application. 

Inorganic Becironlc Speciroseniiy, 2nd ed. Elsevier New York, 1986. Figgis, B. N. In Comprehensive Coordination Chemistry] Wilkinson. C. Cillard, R. 0. McCleveny, J. A., Eds. Pcigemon Oxford. 1987 Vol. 2. Chapter 6. Hggis. B. N. Introduction to UgatuI Fields John Wiley New York. 1966. 

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Schmidtke, H.-H. Vibrational Progressions in Electronic Spectra of Complex Compounds Indicating Stron Vibronic Coupling. 171,69-112 (1994). 

Schmidtke H-H (1994) Vibrational Progressions in Electronic Spectra of Complex Compounds Indicating Stron Vibronic Coupling. J71 69-112 Schmittel M (1994) Umpolung of Ketones via Enol Radical Cations. 169 183-230 Schroder A, Mekelburger H-B, Vogtle F (1994) Belt-, Ball-, and Tube-shaped Molecules. 172 179-201... 

Chapter 11 Coordination Chemistry Bonding, Spectra, and Magnetism 387 Bonding in Coordination Compounds 391 Valence Bond Theory 391 Crystal Field Theory 394 Molecular Orbital Theory 413 Electronic Spectra of Complexes 433 Magnetic Properties of Complexes 459... 

Indirect evidence that electrons are shared between the ligands and the central metal ion comes from the nephelauxetic effect. It is found that the electron-electron repulsion in complexes is somewhat less than that in the free ion. From data derived. from electronic spectra of complexes, separate nephelauxetic series may be set up for... 

Vibrational Progressions in Electronic Spectra of Complex Compounds... 

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